You could run driver cleaner, which should work. If it doesn't (it works a great majority of the time, but sometimes it doesn't, especially in dual boot systems), I'm pretty sure it has directions in the help file re: what to do manually.
Or you could be like every n00b and install every version of catalysts, detonators, forceware, matrox drivers, XGI drivers, etc. and see if that works.
I think I'm going to throw up.